no.
first you have to figure out how many elements you're working with. If you're working with every div on your page, it's simple using
document.getElementsByTagName("div")
then you loop through them. here's a simple example:
Code:
<body>
<input type="button" value ="change divs" onclick="changeDivs()"/>
<div id="myid0" style="background-color:red; width:100px">one</div>
<div id="myid1" style="background-color:red; width:100px">two</div>
<div id="myid2" style="background-color:red; width:100px">three</div>
<script type="text/javascript">
function changeDivs() {
var divs=document.getElementsByTagName("div")
for(var j = 0; j<divs.length; j++){
document.getElementById('myid'+j).style.width= 200+"px";
}
}
</script>
</body>
but I assume from your += that what you want to do is to make them 200 pixels wider than what they already are, and what they already are need not be defined. is that the case?